"any large-scale product that isn't making about 50% markup is probably going to be short-lived."
Yes, I remember the demise of the Kindle well. Selling the base unit at cost price really hampered Amazon, preventing them from doing R&D and thus killing off any possibility of touchscreen versions and colour versions.
Oh, wait - that didn't actually happen, did it?
It's called a loss leader. Amazon make their money from the Kindle by taking a cut of the book sales, just as Apple take their cut from the App Store. I wouldn't expect Apple to sell the iPad or iPhone as a loss leader, but they could definitely sell it for significantly less and still rake in cash hand over fist. It wouldn't be a bad move either - if they cut the price of the iPad by, say, £100 across all lines they'd lock up the tablet market completely.